This invention relates generally to powered jig saws, and particularly to a circuit arrangement for use with such a powered jig saw.
When operating a jig saw having a blade arranged to move along one of predetermined blade locus modes, it is necessary to determine not only the sort of a blade, the rotational speed of the motor which determines the number of blade strokes per unit time but also a most suitable blade locus mode. Furthermore, it is also necessary to determine whether it is necessary to apply coolant oil to the blade. These items have to be determined depending on various pieces of information, such as the sort of the material of a workpiece to be machined or cut, the thickness of the workpiece, a desired finish (rough or fine finish), and a desired way of cutting (straight or curve). To this end some tables showing the relationship between the sort of the material and the sort of blades, and the relationship between the orbital modes and various operating conditions, such as the hardness of the material, the thickness of the workpiece, desired cutting speed, the way of cutting, finish degree, the state of holding the workpiece or the like, are used. However, it is troublesome and time-consuming to finally determine the sort of blade and blade locus mode by using such tables. Furthermore, experiences and the sixth sense are needed to optimally determine these items. Although in some conventional electrical tools, the rotational speed of the motor is automatically controlled by detecting the diameter of the drill bit, such conventional technique cannot be simply adapted to jig saws of the above-mentioned type since the number of necessary information pieces for determining optimum operating condition is large, and since more complicated determination is required.